Getting zapped by SM-58 mic
- Thread starter spleenharvester
- Start date
El Dunco
Sock Supplier to RHCP
I’ve wondered about that. Makes me paranoid I’m one faulty-grounded building away from becoming the ground but with wireless, the most that can go through me is 3 volts.I could go preaching again that the usual grounded strings to abuse the guitarist as a shield is life-threatening nonsense
uOpt
Something Cool
Yeah, wireless helps.
I'm not just concerned about buildings without 3-prog outlet, I am concerned about broken amps that have a problem telling mass/ground and one of the 115V hot wires apart after a defect in a cable or the chassis.
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El Dunco
Sock Supplier to RHCP
Oh boy. I swear I’ve heard a horror story or two of that nature.
I’ve forgotten so much of my small electrics course. Let me get this right. The guitar wiring “ground” is always soldered the bridge. Does that mean it’s going (or could go) through you to ground? That would be the past of least resistance and if I know electricity, it really wants to go to ground.
uOpt
Something Cool
No, it doesn't go through you. It just abuses your belly as a shield for the otherwise unshielded back of the electronics cavity. That shield (you) works even if you have rubber boots on.
In the rubber boots you wouldn't be outright killed by the grounded strings when the amp screws up. It would wait until you touch real ground such as a microphone.
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El Dunco
Sock Supplier to RHCP
Bloody hell!
El Dunco
Sock Supplier to RHCP
Sorry had a typo. In the rubber boot you wouldn't be outright zapped (until you touch the mic).
The nice thing about these zaps is that you muscles in general and left hand in particular cramp up, and that usually means around the guitar neck
You might have just come up with a way to get away with murder by amp malfunction.
spleenharvester
New member
Spoke too soon, it's happening again. At this point I have swapped all power cables and adaptors out for different ones and tested the outlets, so I'm really flummoxed by this.
Only thing I can think of is that possibly it's happening once the tubes in the amp or the mic preamp are warming up, which could be giving the false impression initially that whatever I've done has fixed the problem. Could faulty tubes do this?
EDIT - I think this is actually happening mic preamp-side, if I keep the amp on and unplug the power from the preamp the shocking stops, but if I turn the amp off and leave the preamp on the shocking continues. It also takes about 30 seconds for the shocking to start after the MIC500USB is powered on, regardless of how long the amp has been turned on.
Only thing I can think of is that possibly it's happening once the tubes in the amp or the mic preamp are warming up, which could be giving the false impression initially that whatever I've done has fixed the problem. Could faulty tubes do this?
EDIT - I think this is actually happening mic preamp-side, if I keep the amp on and unplug the power from the preamp the shocking stops, but if I turn the amp off and leave the preamp on the shocking continues. It also takes about 30 seconds for the shocking to start after the MIC500USB is powered on, regardless of how long the amp has been turned on.
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El Dunco
Sock Supplier to RHCP
Leave no stone unturned. Get a multimeter and please, be careful.
spleenharvester
New member
I've pulled the amp apart for some testing. Here are my findings:
Does this give any clues?
- Measured live > chassis ground and neutral > chassis ground. Meter reads OL, which according to this means there's an issue?
- Having trouble figuring out the power transformer pinout, there's no data sheet for it anywhere. Am I correct to interpret it's a single primary with two secondaries? Black-White reads 122ohm, Red-Red reads 253ohm, but Blue-Blue reads 4ohm.
- I am getting 98ohm from green to chassis ground, but I get continuity between green and the input jack.
Does this give any clues?
spleenharvester
New member
Fixed it. I mean, actually fixed it this time. It was the cheap shitty power supply that came with the MIC500USB, which has no earth pin. I thought I'd tried a different one but apparently not. Replace it with a good quality one with an earth pin - no shocks. Go back to the original - non-contact voltage tester goes nuts. Rinse and repeat.
The model is TCHELICON ADS-12AE-12 12012E if anyone wants to avoid it like the plague.
The model is TCHELICON ADS-12AE-12 12012E if anyone wants to avoid it like the plague.
LLL
New member
Behringer strikes again.
